The role of food in health and disease is of immense and ongoing interest. One of the most studied botanicals is soy. Soy has been reported to have protective effects against breast cancer in Asian women. At least two studies have evaluated the effect of soy isoflavones on the breast using NAF, one (Hargreaves et al., 1999) short term (2 weeks) and the other (Petrakis et al., 1996) for a longer duration (6 months). The short-term study administered 45 mg soy isoflavones to 84 healthy premenopausal women. They found that the isoflavones genistein and daidzein were concentrated in NAF compared to matched serum, both before and after soy supplementation, and that apolipoprotein D (apoD) levels were significantly lowered and pS2 levels were raised in response to soy ingestion (pS2 levels rise and apoD levels go down in response to estrogen; Harding et al., 2000). NAF cytology did not significantly change. In the longer-term study, which evaluated both pre- and postmenopausal white subjects, the effect of soy protein isolate containing 38 mg of genistein was assessed by NAF volume, cytology, and gross cystic disease fluid protein (GCDFP-15) levels (Petrakis et al., 1996) before and after taking soy protein isolate. There was little effect of soy on the NAF parameters in postmenopausal women. In premenopausal women, there was a two- to sixfold increase in NAF volume, a moderate decrease in GCDFP-15 levels, and evidence of epithelial hyperplasia, which was not seen before soy ingestion, as well as increased levels of plasma estradiol, suggesting that isoflavones in soy provided an estrogenic stimulus.
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